igneous
Pumice
Pumice (Felsic Volcanic Glass)
Mohs hardness: 5 - 6; Color: Light gray, off-white, cream, or pale tan; Luster: Dull to vitreous; Structure: Vesicular, cellular, glassy texture; Specific Gravity: Very low (typically < 1.0, enabling it to float on water)
- Hardness
- 5 - 6
- Color
- Light gray, off-white, cream, or pale tan
- Luster
- Dull to vitreous
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Physical properties
Mohs hardness: 5 - 6; Color: Light gray, off-white, cream, or pale tan; Luster: Dull to vitreous; Structure: Vesicular, cellular, glassy texture; Specific Gravity: Very low (typically < 1.0, enabling it to float on water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma rapidly expands and cools into a porous, glassy rock. Found worldwide in regions with active or ancient explosive volcanism.
Uses & applications
Widely used as an abrasive in soaps, polishers, and cosmetic stone tools (pumice stone), as lightweight aggregate in concrete, and as a soil conditioner in horticulture.
Geological facts
Pumice is one of the few rocks that can float on water due to its extremely high porosity and tiny sealed gas cavities created by trapped volcanic steam and gases during rapid cooling.
Field identification & locations
Identified by its extremely light weight, pale light color, coarse sponge-like texture, and ability to float on water. Very common near volcanic arc deposits.
